The lsmem command lists the ranges of available memory with their online status. The listed memory blocks correspond to the memory block representation in sysfs. The command also shows the memory block size and the amount of memory in online and offline state.
The default output is compatible with original implementation from s390-tools, but it’s strongly recommended to avoid using default outputs in your scripts. Always explicitly define expected columns by using the --output option together with a columns list in environments where a stable output is required.
The lsmem command lists a new memory range always when the current memory block distinguish from the previous block by some output column. This default behavior is possible to override by the --split option (e.g., lsmem --split=ZONES). The special word "none" may be used to ignore all differences between memory blocks and to create as large as possible continuous ranges. The opposite semantic is --all to list individual memory blocks.
Note that some output columns may provide inaccurate information if a split policy forces lsmem to ignore differences in some attributes. For example if you merge removable and non-removable memory blocks to the one range than all the range will be marked as non-removable on lsmem output.
Not all columns are supported on all systems. If an unsupported column is specified, lsmem prints the column but does not provide any data for it.
Use the --help option to see the columns description.
- -a, --all
List each individual memory block, instead of combining memory blocks with similar attributes.
- -b, --bytes
Print the sizes in bytes rather than in a human-readable format.
By default, the unit, sizes are expressed in, is byte, and unit prefixes are in power of 2^10 (1024). Abbreviations of symbols are exhibited truncated in order to reach a better readability, by exhibiting alone the first letter of them; examples: "1 KiB" and "1 MiB" are respectively exhibited as "1 K" and "1 M", then omitting on purpose the mention "iB", which is part of these abbreviations.
- -J, --json
Use JSON output format.
- -n, --noheadings
Do not print a header line.
- -o, --output list
Specify which output columns to print. Use --help to get a list of all supported columns. The default list of columns may be extended if list is specified in the format +list (e.g., lsmem -o +NODE).
Output all available columns.
- -P, --pairs
Produce output in the form of key="value" pairs. All potentially unsafe value characters are hex-escaped (\x<code>).
- -r, --raw
Produce output in raw format. All potentially unsafe characters are hex-escaped (\x<code>).
- -S, --split list
Specify which columns (attributes) use to split memory blocks to ranges. The supported columns are STATE, REMOVABLE, NODE and ZONES, or "none". The other columns are silently ignored. For more details see Description above.
- -s, --sysroot directory
Gather memory data for a Linux instance other than the instance from which the lsmem command is issued. The specified directory is the system root of the Linux instance to be inspected.
- -h, --help
Display help text and exit.
- -V, --version
Print version and exit.
This option controls summary lines output. The optional argument when can be never, always or only. If the when argument is omitted, it defaults to "only". The summary output is suppressed for --raw, --pairs and --json.
lsmem was originally written by Gerald Schaefer for s390-tools in Perl. The C version for util-linux was written by Clemens von Mann, Heiko Carstens and Karel Zak.
For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.
The lsmem command is part of the util-linux package which can be downloaded from Linux Kernel Archive.